The goal of this project is to evaluate the feasibility, acceptability, and effect size of a new computerized Motivational Enhancement Therapy (cMET) intervention for alcohol-involved adolescents in primary care. We previously developed a computerized screening and provider brief advice system for primary care, and compared it to treatment as usual (TAU) among 2096 12- to 18-yr-old patients. We found a large reduction in overall drinking rates at 3-months for the active condition versus control and the effect was still detectable at 12-months. Nonetheless, the majority of baseline drinkers continued to drink, demonstrating the need for a more robust intervention than provider brief advice alone. In a parallel line of research, we adapted Motivational Enhancement Therapy (MET) to be developmentally-appropriate for adolescents and practical for delivery in 2- to 3-sessions by a trained counselor in busy outpatient medical settings, and conducted a randomized trial comparing standard care (SC) vs. SC+MET among 12- to 21-yr-olds (N=140) in our outpatient substance abuse evaluation and treatment program. We found that SC+MET patients had significantly greater treatment adherence and reduced rates of driving and riding risks during the 9-month follow-up. To promote its transferability to primary care settings that reach many more adolescents, we created an interactive, computerized version of MET (cMET) with customizable avatars for the teen and clinicians, interactive electronic versions of all MET worksheets, and secure patient-clinician email communication and notifications. The program also generates monthly provider-to-teen health-promotion messages to extend the intervention effect over time. The cMET program is completed in two <1-hr sessions; the first completed adolescents will complete as soon as possible after the medical visit, and the second 2 weeks later on a private computer at home or elsewhere. Patients return for a check-in visit with their provider 4 weeks after completing session 2. We are now prepared to conduct a Stage-1 randomized controlled pilot study of the cMET system, with its enhanced standardization and efficiency, compared to treatment as usual, among 14- to 20-yr-old screen+ primary care patients. Our study aims are to: 1) Assess cMET feasibility and acceptability and estimate its effect size on underage drinking. Feasibility: teen completion of cMET exercises, cMET sessions 1 and 2, and follow-up visits; Acceptability: adolescent and provider satisfaction; Effect Size Estimate: compare cMET vs. TAU rates of alcohol use at 3-, 6-, and 9-month follow-ups. Hypothesis: Among 14- to 20-yr-old primary care patients, those receiving cMET will have lower rates of any alcohol use, days of alcohol use, drinks per drinking day, and days of heavy episodic drinking, than those receiving treatment as usual. 2) Estimate effect sizes for tobacco, cannabis, and other drug use, and other substance-related risks and outcomes. 3) Identify potential moderators and mediators of cMET's effect.